2 ml of overnight culture is sufficient for 26 transformations. The culture can be kept at 4°C
for one week and used for preparation of competent cells.
• The day of transformation pre-warm culture tubes containing the required amount of
C-medium (1.5 ml for each 2 transformations) at 37°C for at least 20 min. Pre-warm LB
agar plates, supplemented with ampicillin, X-Gal and IPTG (see recipes on p. 15) in a 37°C
incubator for at least 20 min before plating